Charcot-Marie-Tooth is a hereditary motor and sensory neuropathy. Due to CMT being an inherited disorder, their is almost always a family history of the disorder, however on occasion random mutations can result in presentation of CMT. It is the most common inherited neuropathy.
The pathophysiology of CMT varies according to the genetic abnormality present. CMT 1 typically involves the spontaneous break down of the myelin sheath surrounding the axon (demyelinating), resulting in slower conduction of motor and sensory nerves. Responding to demyelination, schwann cells respond by rebuilding myelin. This demyelination and rebuilding leads to a so-called ‘onion bulbing’ of the axon. As the nerves of the spinothalamic tract are unmyelinated (pain and temp), these are unaffected. CMT 2 typically involves the death of the axon (axonal neuropathy) and therefore is not demyelinating. CMT 3 is essentially a more severe form of CMT 1, with severe demyelination and typical onset of symptoms is younger.
Symptoms and Clinical Features
Symptoms usually present at childhood/ adolescence, however have been known to present later in adulthood. Symptoms may include difficulty walking, clumsiness when running, and the presence of a ‘foot drop‘ or ‘steppage gait’.
In addition, wasting of the distal muscles will likely result in the presence of the so called ‘inverted champagne bottle‘ or ‘stork leg’. High foot arches are associated with CMT and patients may therefore struggle to find suitable footwear. Overuse of hands and limbs may also result in spasm/ cramping. Pregnancy has been known to exacerbate symptoms of CMT.
Deep tendon reflexes will likely be absent or markedly reduced, typically disappearing in the Patellar and Achilles reflexes first. Wasting of the distal muscles may be present, giving rise to the ‘inverted champagne bottle leg’ as described above. High foot arches (pes cavus) will likely also be present.
Sensory nerve involvement usually results in reduced sensation of vibration and proprioception ability is usually poor
Diagnosis is usually made with consideration of findings arising from the neurological examination and from detailed history/ family history. Confirmatory diagnosis can be made by Electromyelography/ Nerve Conduction Studies, which will (depending on CMT genetic variant) show a slowing of condition in the motor and sensory nerves. Nerve Biopsy is not typically performed for diagnosis, however would show features typical of each CMT variant; onion bulbing in CMT 1, axon loss in CMT 2, or thinning of myelin in CMT 2. In addition, Genetic Testing is available to aid diagnosis.
Treatment typically consists of referral to a physiotherapist early on in the diagnosis in order to maintain muscle strength and reducing wasting. Orthotics may be necessary to correct for high foot arches, and podiatry referrals may be necessary for foot-care and removal of callouses due to abnormal gait. Surgery is sometimes also used to correct foot and joint deformities.